ES2811761T3 - Particulate phyllosilicate material - Google Patents

Abstract

A ground phyllosilicate mineral comprising particulate talc having a d50 in the range of 0.5 to 10 μm and a shape factor of 10 to 100, where the shape factor is the measure of the ratio of particle diameter to particle thickness, for a population of varying size and shape, as measured using electrical conductivity methods, apparatus, and equations described in US document No. 5,576,617.

Description

DESCRIPTION

Particulate phyllosilicate material

Field of the invention

The present invention relates to ground phyllosilicate and the use thereof.

Background of the invention

Aqueous suspensions containing pigments or plate minerals, such as the phyllosilicate minerals kaolin and talc, are widely used in various applications. These include, for example, the production of compositions containing pigment or filler material, which can be used in the manufacture of paper or paper coating, and in the production of compositions for paints, plastics and the like.

Typically, natural sources of plate minerals comprise stacks of particles, in which the individual particles are loosely bound to one another. These piles are created by chemical processes during the pigment creation process (for example, kaolin is produced by exposing clays or feldspar to the elements in hot, humid conditions). In the preparation of products for industrial use, these natural materials are typically processed by grinding an aqueous suspension of the material in the presence of a hard grinding medium (eg ceramic spheres or sand).

Current practice is to process the raw material by suspending the product in water, at relatively low solids (typically <40% dry content). This facilitates the removal of contaminants, the application of chemical treatments (eg bleaching to improve color) and the refinement of the product to a target particle size. Low solids content is also required because a combination of increasing particle shape factor (also referred to as "aspect ratio") and no dispersant or very low level of dispersant means that the viscosity would be too high for normal operations. processing (eg pumping, mixing, etc.). The water is then removed from the product and the product is dried, so that it can be sold as a dry powder (<3% humidity), a granulate (10-20% humidity) or a dispersed liquid paste (25-40% moisture).

WO 00/59841 A1 teaches kaolin raw materials for producing novel kaolin clay pigments, especially useful for coating light and ultra-light paper for gravure and offset printing, thereby using a kaolin green having a quantity desired from non-kaolin phyllosilicate clay minerals, to produce mechanically delaminated kaolin coating pigments.

WO2004 / 061014 A1 teaches a kaolin composition having improved physical properties for use in the production of paper products. The composition may comprise kaolin having a shape factor of at least 20 and a particle size distribution such that at least 94% by weight of the kaolin has an esd of less than 2 µm. A method for manufacturing kaolin product from sedimentary kaolin is also disclosed.

WO 02/16511 A1 relates to a method for the production of a particulate kaolin material, which is suitable for use with improved SC filler material. The method further includes different steps for the preparation of an aqueous suspension of feed of a kaolin fraction in which no more than 10% has a particle size of 10 µm or greater and no more than 10% has a smaller particle size. than 0.25 jm.

WO 2004/016697 A2 teaches a kaolin pigment product derivable from crude kaolin obtained from a secondary kaolin deposit, for use in coating compositions to provide a gloss coating on paper. The pigment product comprises a particulate processed kaolin, having a particle size distribution such that at least about 85% by weight of the particles have an equivalent spherical diameter of 2 µm or less.

Document US6348536B1 discloses a process for treating a sheet-type mineral, in the form of particles made up of piles of sheets, to obtain a functional filler for a polymer material. Furthermore, it is disclosed that the mineral is suspended in a liquid and is subjected to a delamination process, after which a particle size smaller than the initial particle size is obtained. The remaining talcum powder can be incorporated as a filler in thermoplastics, improving physical properties.

Two processes occur during grinding. Individual particles can separate from the stack, due to delamination, thus leading to an increase in form factor. The particles can break or break as well, leading to a reduction in the form factor. At lower solids, delamination dominates, so there is a significant increase in form factor.

Furthermore, when processing occurs at a low solids content, the water then has to be removed to obtain the final product form (eg high solids liquid paste, granulate or spray drying). It may also be necessary to further subject the product to centrifugation, to remove coarse particles. This additional processing adds to the amount of equipment and machinery required (increased capital expenditure) and reduces the yield of the inorganic particulate material.

Summary of the invention

The invention relates to a ground phyllosilicate mineral comprising talc, having a d50 in the range of 0.5 to 10 µm and a form factor of 10 to 100.

In a first aspect, a method for grinding an inorganic particulate material is provided, comprising:

(i) supplying an aqueous suspension comprising a particulate phyllosilicate mineral having a shape factor of less than 60; Y

(ii) grinding the aqueous suspension to form a ground product,

wherein the particulate phyllosilicate mineral is present in the aqueous suspension in an amount greater than 55% by weight.

In a second aspect, a method for grinding an inorganic particulate material is provided, comprising:

(i) supplying an aqueous suspension comprising a particulate phyllosilicate mineral having a shape factor of less than 60; Y

(ii) grinding the aqueous suspension using a tumble mill, stirred mill, stirred medium decanter, or tower mill, to form a ground product,

wherein the particulate phyllosilicate mineral is present in the aqueous suspension in an amount greater than 45% by weight.

In the said first and second aspects, the form factor of the phyllosilicate mineral in the product may be less than the form factor of the phyllosilicate mineral in the aqueous suspension before grinding, or it may be approximately the same as the factor of form of the phyllosilicate mineral in the aqueous suspension before grinding, or may be greater than the form factor of the phyllosilicate mineral in the aqueous suspension before grinding.

Furthermore, the disclosure relates to a phyllosilicate ground mineral comprising particulate kaolin having a d50 in the range of 0.1 to 5 µm and a form factor of 10 to 100.

It has been found that by milling, at relatively high solids content, an inorganic phyllosilicate mineral that has been selected for having a relatively low form factor can lead to significant benefits. In particular, milling a dispersed suspension of the phyllosilicate to a high solids content means that no dewatering or drying is required.

Furthermore, improvements can be obtained in the steepening of the formed product, and its gloss. Also, when only talc (i.e. 100% talc) is ground or a talc / kaolin mixture is ground together to high solids, it is possible to dispense with the need for a surfactant, or wetting agent, which is typically used when producing a liquid talcum paste with high solids content. In addition, a co-milled liquid talc / kaolin paste is more stable (i.e. has less chance to settle or gel) and has better solids / viscosity performance, compared to a liquid talc paste.

The level of coarse particles in the high solids ground product has also been found to be low enough that the product can be used directly in the paper coating, without a centrifugation step. Typically, a centrifugation step may be required to remove coarse particles from ground products that have been prepared by milling phyllosilicate minerals, in order not to give rise to adverse sag effects in the high speed paper coating process. In certain embodiments of the invention, such a centrifugation step can be eliminated.

Furthermore, inorganic phyllosilicate materials, such as talc, can be produced by certain embodiments of the methods of the present disclosure, to have fine particle size (eg, reduced) and average shape factors (eg, factors less than wet ground talc by previous methods, although greater than dry ground talc).

Detailed description

The present invention provides the aspects mentioned above. Optional and preferred features and embodiments of the different aspects are also described. Unless stated otherwise, any optional or preferred feature or embodiment may be combined with any other optional or preferred feature or embodiment, and with any of the aspects of the invention mentioned herein.

The particle size characteristics described herein are measured by sedimentation of the particulate material, in a fully dispersed condition in an aqueous medium in a Sedigraph 5100 apparatus for particle size analysis supplied by Micrometrics Instruments Corporation Norcross, Ga, USA. The Sedigraph 5100 provides measurements and a graph of the cumulative weight percent of particles having a size referred to in the art as the "equivalent spherical diameter" (esd).

The "shape factor", as used herein, is a measurement of the ratio of particle diameter to particle thickness, for a population of particles of varying size and shape, as measured using the methods, apparatus, and equations of electrical conductivity described in US document No. 5576617. As the technique for determining the form factor further described in the '617 patent, the electrical conductivity of a composition of an aqueous suspension of oriented particles under test is measured, as the composition flows through a container. Electrical conductivity measurements are taken along one container direction and along another container direction, transverse to the first direction. The form factor of the particulate material under test is determined using the difference between the two conductivity measurements.

The term "d50" used herein refers to the median particle diameter and is the particle diameter at which 50% by weight of the product is greater and 50% by weight is less.

The "steepening" of a particle size distribution, as referred to herein, is calculated by 100 x d30 / d70 (d30 is the size at which 30% by weight of the product is larger and 70% is smaller, d70 is the size at which 70% by weight is larger and 30% smaller).

The term "solids" used herein refers to pigment in a liquid pigment-water paste, unless the context is defined otherwise.

Phyllosilicate mineral feed material

The phyllosilicate mineral used in certain embodiments can be selected from kaolin, talc, and mica. In one embodiment, a single phyllosilicate mineral is used in order to produce a ground material comprising only the phyllosilicate mineral. For example, the individual phyllosilicate mineral may be kaolin or the individual phyllosilicate mineral may be talc. In another embodiment, a mixture of two or more phyllosilicate minerals can be co-ground or milled. For example, a mixture of kaolin and talc can be eaten, using the method of certain embodiments disclosed herein. When using a mixture of kaolin and talc, the weight ratio of kaolin to talc is in the range of 95: 5 to 5:95, for example in the range of preferably between 50:50 and 90:10.

The form factor of the "feed" phyllosilicate mineral in the aqueous suspension is less than 60, for example less than 50 or less than 40, or less than 30, or less than 20, or less than 15. The form factor of the phyllosilicate feed mineral may be less than 60 and greater than 5, or it may be greater than 10, or it may be greater than 15. In one embodiment, the feed mineral is talc having a form factor of 10 to 45 , or 15 to 35. In another embodiment, the feed mineral is kaolin having a form factor of 10 to 50.

When kaolin is present in the feed, it may have a d50 in the range of 0.1 to 20 µm, for example in the range of 0.1 to 10 µm, for example in the range of 0.1 to 5 µm. The steepness value of kaolin used in the feed ore can be in the range of 10 to 50.

In one embodiment, the feedstock is kaolin having a form factor of 10 to 50 and at d50 in the range of 0.1 to 5 µm.

When talc is present in the feed, it may have a d50 in the range of 2 to 20 µm, for example in the range of 2 to 15 µm, for example in the range of 2 to 10 µm.

The steepening value of the talc used as the feed mineral may be in the range of 15 to 40, for example 25 to 35.

The talc can have a whiteness of at least about 50, or at least about 60 or at least about 70, as measured using a MinoltaChromameter CR300 using illuminant D65 and a 2 ° measurement geometry.

Talc can have a particle size distribution such that no more than 50% by weight of the particles is smaller than 2 µm. In one embodiment the talc can have a particle size distribution such that no more than 40% by weight of the particles is smaller than 2 µm. In another embodiment, the talc may have a particle size distribution such that no more than 35% by weight of the particles is smaller than 2 µm. In another embodiment, the talc can have a particle size distribution such that no more than 30% by weight of the particles is smaller than 2 µm. In still another embodiment, the talc may have a particle size distribution such that no more than 25% by weight of the particles is smaller than 2 µm. In one embodiment, the talc can have a particle size distribution such that no more than 20% by weight of the particles is smaller than 2 µm. In certain embodiments, the talc can have a particle size distribution such that no more than 15% by weight of the particles is smaller than 2 µm.

In one embodiment, the feedstock is talc having a form factor of 15 to 35 and a d50 in the range of 2 to 20 µm, for example in the range of 2 to 10 µm.

In the first aspect, the particulate phyllosilicate feedstock is present in the aqueous suspension in an amount greater than 55% by weight, for example greater than 60% by weight, or greater than 65% by weight. In certain embodiments, the phyllosilicate feed mineral is present in an amount of no more than 70% by weight. In one embodiment, particulate phyllosilicate feed mineral is present in the aqueous suspension in an amount of 55 to 65% by weight.

In the second aspect, the particulate phyllosilicate feed mineral is present in the aqueous suspension in an amount greater than 45% by weight, for example greater than 50% by weight, or greater than 55% by weight, or greater than 60 % by weight, or greater than 65% by weight. In certain embodiments, the phyllosilicate feed mineral is present in an amount no greater than 70% by weight. In one embodiment, the particulate phyllosilicate feed mineral is present in the aqueous suspension in an amount of 55 to 65% by weight.

In addition to the phyllosilicate mineral present in the aqueous grinding slurry, one or more other particulate minerals may be present. In one embodiment of the invention, the only particulate mineral present in the aqueous suspension is the phyllosilicate mineral. Thus, in such embodiments no additional particulate mineral is present.

The phyllosilicate mineral for use as a feed material can be a preparation of the raw material, by one or more pre-processing steps. For example, raw materials can be processed in aqueous suspension to remove contaminants and impurities, for example by magnetic separation. The raw material can also be bleached using methods known to those skilled in the art. Also the raw material can be subjected to a preliminary process to reduce the particle size of the agglomerated raw material. For example, the raw material can be crushed or ground to reduce the particle size to the desired particle size of the feedstock. In certain embodiments where the phyllosilicate mineral is talc, the feedstock may be subjected to an initial dry milling step. In certain embodiments where the phyllosilicate mineral is kaolin, the feedstock may be subjected to an initial wet milling step.

The slurry comprising the pre-processed coarse material may be dewatered by, for example, use of a tube press, although other dewatering methods such as thermal or spray drying are also contemplated. In certain embodiments, the water removed may have a suitable high solids content, corresponding to that desired for the milling step.

In alternate embodiments, the water removed product can be dispersed, using a suitable dispersing agent.

Suitable dispersing agents are chemical additives capable, when present in a sufficient quantity, of acting on the particles of the particulate material, to effectively prevent or restrict flocculation or agglomeration of the particles to a desired extent, in accordance with normal requirements of prosecution. The dispersant can be present at levels up to about 1% by weight, and includes, for example, polyelectrolytes such as polyacrylates and copolymers containing polyacrylate species, especially polyacrylate salts (for example, sodium and aluminum optionally with a metal salt Group II), sodium hexametaphosphates, nonionic polyol, polyphosphoric acid, condensed sodium phosphate, nonionic surfactants, alkanolamines and other reagents commonly used for this function. The dispersant can be selected, for example, from conventional dispersant materials commonly used in the processing and milling of inorganic particulate materials. Such dispersants will be well recognized by those skilled in the art. They are generally water soluble salts capable of supplying anionic species which in their effective amounts can be adsorbed onto the surface of the inorganic particles and thereby inhibit the aggregation of the particles. Unsolvated salts suitably include alkali metal cations such as sodium. In some cases solvation can be assisted by making the aqueous suspension slightly alkaline. Examples of suitable dispersants include: water-soluble condensed phosphates, for example, polymetaphosphate salts [general form of sodium salts: (NaPO3) x] such as tetrasodium metaphosphate or so-called "sodium hexametaphosphate"(Graham'ssalt); water soluble salts of polysilicic acids; polyelectrolytes; salts of homopolymers or copolymers of acrylic acid or methacrylic acid, or salts of polymers of other derivatives of acrylic acid, which suitably have a weight average molecular mass of less than about 20,000. Sodium hexametaphosphate and sodium polyacrylate are especially preferred, the latter suitably having a weight average molecular mass in the range of about 1,500 to about 10,000.

In certain embodiments of the invention, the talc is ground alone or is co-ground with kaolin, in the absence of any surfactant species. This reduces and simplifies the dispersant system required during milling. Typically, in order to make a high solids liquid talc paste, in addition to the presence of a dispersant, a surfactant is included and the pH is kept relatively high. However, it was found that when the mixture is manufactured before milling, talc can be added to a liquid kaolin paste, without the need for any surfactant, although it may be necessary to include an additional amount of dispersant, typically the same as used to reprocess kaolin.

In certain embodiments of the method disclosed herein, it has been found that the addition of a thickening agent to the suspension is not necessary. Therefore, in certain embodiments of the invention, milling is carried out in the absence of any thickening agent.

Grinding the aqueous suspension

The aqueous suspension of phyllosilicate feedstock is subjected to milling. grinding is desirably carried out by abrasion using a particulate grinding medium. alternatively, the suspensions can be ground by autogenous milling, that is, in the absence of a milling medium. When used, the particulate grinding medium, when present, can be of a natural or a synthetic material. The grinding medium can comprise, for example, balls, spheres or pellets of any hard material, ceramic or metallic material; Such materials can include, for example, alumina, zirconia, zirconium, silicate, aluminum silicate, or the mulite-rich material that is produced by calcining kaolinitic clay at a temperature in the range of about 1300 ° C to about 1800 ° C. Alternatively, natural sand particles of a suitable particle size can be used.

The grinding can be carried out in one or more stages. For example, the feed slurry may be partially ground in a first abrasive chopper, with the suspension of partially ground inorganic particulate material then fed to a second abrasive chopper for further grinding, after which the slurry of the ground material it can be fed to one or more subsequent abrasive mincers.

During milling additional dosages of dispersing agent can be added, as required to maintain a fluid suspension.

The grinding energy applied during grinding can be at least 25 kWh / t, for example at least 50 kWh / t, at least 100 kWh / t, at least 150 kWh / t, at least 200 kWh / t, at least 250 kWh / t, at least 300 kWh / t, or at least 500 kWh / t.

After milling is complete, any milling media can be removed, and water can be removed from the product slurry, if required. In some embodiments of the invention, the solids content of the slurry is focused after milling is complete, to be the final desired solids content in the product, in which case no further removal of water is required, and in particular may dispense with a thermal drying step. For example, in an embodiment in which the phyllosilicate mineral comprises kaolin, the kaolin feedstock can be prepared by a method in which water removal is achieved only by tube compression and the milling step is performed with high solids to produce the slurry with the required final level of target solids. In another embodiment in which the phyllosilicate mineral in the slurry to be ground is 100% kaolin, the kaolin feedstock can be prepared by a method in which removal of water is achieved only by tube compression and the high solids milling step is executed to produce the slurry with the required final level of target solids. This avoids costly thermal drying.

The grinding can be carried out in a suitable grinding device. In certain embodiments, the grinding device can be an open mill having a vertical axis, without recirculation of the slurry. TO By way of example, the grinding device can be a tumbling mill (eg rod, ball and autogenous), a stirred mill (eg SAM, GK mill, or IsaMill), a mesh mill such as a decanter stirred medium (SMD), or a tower mill. In certain embodiments, the use of a stirred mill decanter is preferred. Additional information on stirred mills can be found in the textbook "Wills' Mineral Processing Technology", 7th edition, chapter 7, the contents of which are incorporated herein by reference for all purposes.

Phyllosilicate Ground Mineral Product

In one embodiment, the ground product obtained by grinding the aqueous suspension of the phyllosilicate mineral has a form factor that is approximately the same or is reduced, compared to that of the feed material. This may be the case when the feed mineral particles are relatively thin and have a high aspect ratio, for example when the feed has already been completely delaminated (so that no further increase in form factor is possible). The maximum shape factor can be between 10 and 45, for example between 12 and 40.

In another embodiment, the ground product obtained by grinding the aqueous suspension of the phyllosilicate mineral has an increased shape factor compared to that of the feed material. The form factor can be increased by at least 50% or at least 100%, and can depend on, for example, the origin of the mineral. Thus, some deposits may have a higher proportion of particle stacks compared to others, and thus may give a greater increase in form factor. In embodiments, the increased shape factor will be less than 100, or less than 80 or less than 60 or less than 50. When the ground product is a mixture of phyllosilicate minerals, there is increased shape factor of each phyllosilicate mineral. in the mixture, and the increased form factor (or other property) is measured on the mixture of minerals, compared to the form factor of the mixture of phyllosilicate minerals in the feed.

When the phyllosilicate mineral comprises kaolin, the form factor of kaolin in the product is greater than the form factor of kaolin in the feedstock, and is in the range of 10 to 100, for example in the range of 10 to fifty.

When the phyllosilicate mineral comprises talc, the form factor of talc in the product is greater than the form factor of talc in the feedstock, and is in the range of 10 to 100, for example in the range of 20 to 70, or in the range of 30 to 60, or in the range of 40 to 50.

When the phyllosilicate mineral comprises kaolin, the d50 of kaolin in the product is, for example in the range of 0.1 to 10 | jm, for example in the range of 0.1 to 5 | jm, for example in the range of 0.1 to 3 | jm.

When the phyllosilicate mineral comprises talc, the d50 of talc in the product is, for example in the range of 0.1 to 20 jim, for example in the range of 0.5 to 10 jim, for example in the range of 0.5 to 6 jim or in the range of 1.0 to 5 jim, or in the range of 1.5 to 4 jim.

The solids content of the resulting aqueous suspension after milling will be determined by the solids content of the aqueous suspension of the feedstock. Due to evaporation of water during milling, the solids content of the resulting aqueous suspension after milling may be higher than that of the feedstock, unless additional water is added during milling, to maintain a desired content of solid.

The ground phyllosilicate mineral obtained by the methods disclosed herein is another aspect. Thus, certain embodiments also supply a particulate kaolin, optionally in aqueous suspension, having a d50 in the range of 0.1 to 5 jim and a form factor of 10 to 100, for example a d50 is in the range of 0.4 to 2.5 jim and a form factor is in the range of 10 to 50. In certain embodiments, the invention provides a particulate talc, optionally in aqueous suspension, having a d50 in the range of 0.5 to 10 jim and a form factor of 10 to 100, for example a d50 in the range of 1.0 to 6.0 jim and the form factor is in the range of 20 to 70.

Examples of embodiments of the invention

In one embodiment, the phyllosilicate feed mineral is kaolin having a form factor of 10-20 and a d50 of 2 jim or greater, for example a form factor of 15 to 20 and a d50 of 2 to 5 jim. Milling is performed at 55% by weight solids, or higher. The product mineral has a form factor greater than 25, or greater than 30, or greater than 40 or greater than 50, and has a d50 of 1.5 jim or less.

In another embodiment, the phyllosilicate feed mineral is kaolin having a form factor of 5-15 and a d50 of 0.5 jim or greater, for example a form factor of 10 to 15 and a d50 of 0.5 to 2jim. Grinding is performed at 55 wt% solids or greater. The product mineral has a form factor that is roughly the same as the form factor of the feed mineral, or has a form factor that is greater than the form factor of the feed mineral, for example greater than 15, or greater than 20, or greater than 25 or greater than 30. Also, the product ore has a d50 less than 0.5 | jm.

In another embodiment, the phyllosilicate feed mineral is talc having a form factor of 10-30 and a d50 of 5 µm or greater, for example a form factor of 15 to 25 and a d50 of 5 to 10 µm. Milling is performed at 55% by weight solids or more. The product ore has a form factor greater than 40, or greater than 50, or greater than 60. Also, the product ore has a d50 less than 5 jm.

In another embodiment, the phyllosilicate feed mineral is talc having a form factor of 30-50 and a d50 of 2 µm or more, for example a form factor of 35 to 45 and a d50 of 2.5 to 5 µm. Milling is performed at 55% by weight solids or more. The product ore has an increased form factor of greater than 40, or greater than 45, or greater than 50. In addition, the product ore has a decreased d50 of less than 2.5 jm.

In another embodiment, the phyllosilicate feed mineral is a mixture of kaolin and talc in a weight ratio of 1: 1 to 5: 1, in which the talc has a form factor of 10-30 and a d50 of 5jm. or greater, and kaolin has a form factor of 10-30 and a d50 of 2 jm or greater. Milling is performed at 55% by weight solids or more. The product ore has an increased form factor greater than 30, or greater than 40. Also, the mixed product ore has a decreased d50 less than 2.5 jm.

Uses of ground particulate material

The ground particulate material obtained using certain embodiments of the methods disclosed herein can be used in a wide variety of applications, as will be readily apparent to one of ordinary skill in this art. In certain embodiments, the inorganic particulate material is present as a coating or filler pigment, or as part of a coating or filler composition. Applications include, for example, the preparation of: paper (which term includes within its scope all forms of paper, card, poster, cardboard and the like, including without limitation printing paper and writing paper); polymers and rubbers, for example plastics (which can be in the form of a film); paintings; sealants and putties; ceramics; as well as compositions that are subsequently processed to obtain any of the above.

Particular embodiments of the present invention will now be described, with reference to the following non-limiting examples and accompanying drawings.

Examples

Example 1

A feed kaolin having a d50 of 2.1 jm, a particle content having an esd of 2 jm or less, 48% by weight, a steepening of 31 and a form factor of 17, was prepared in aqueous suspensions. completely dispersed, having a solids content of 30% and 60% by weight. The dispersing agent was a sodium polyacrylate dispersant.

The suspensions were abrasive ground using a medium size high density milling medium (8/14), with varying amounts of energy input. Table 1 below shows the results obtained.

Table 1

(continuation)

Example 2

The method of Example 1 was used to grind a different kaolin feed. The kaolin used had a d50 of 0.86 | jm, a particle content having an esd of 2 | jm or smaller, 70% by weight, a steepening of 21, and a form factor of 11. In Table 2 below the results obtained are presented.

Example 3

The method of Example 1 was used to grind a different kaolin feed. The kaolin used had a d ⁵⁰ of 0.56 jm, a particle content having an esd of 2 jm or smaller, 90% by weight, a steepening of 36, and a form factor of 12. Table 3 below shows present the results obtained.

Table 2

Table 3

Example 4

A feed talc was prepared having a d50 of 8.4 | jm, a particle content having an esd of 2 | jm or smaller, 13% by weight, a steepening of 31, and a form factor of 21, in a fully dispersed aqueous suspension having a solids content of 60% by weight. The same dispersing agent was used that had been used to prepare the kaolin suspensions.

The suspension was milled using a medium size high density milling medium (8/14), with varying amounts of energy input. Table 4 below shows the results obtained.

For comparison, results for a dry processed talc and a commercially available wet ground talc were also included.

Table 4

Example 5

Example 4 was repeated using a different talc, having a form factor of 20, a d50 of 7.55jm, and a particle content having an esd of 2 µm or less, of 13% by weight. The results obtained are shown in Table 5 below 5. The solids content was 60% by weight.

Table 5

Example 6

Example 4 was repeated using a different talc, having a form factor of 39, a d50 of 2.96 µm, and a particle content having an esd of 2 µm or less, of 35% by weight. The results obtained are shown in Table 6 below 6. The solids content was 57% by weight.

Table 6

Example 7

Example 4 was repeated using a mixture of 75% by weight kaolin and 25% by weight talc. the total solids content in the aqueous suspension for grinding was 64% by weight.

Table 7 below shows the characteristics of the feed kaolin and feed talc, together with the results obtained.

Table 7

Claims (15)

1. A ground phyllosilicate mineral comprising particulate talc having a d50 in the range of 0.5 to 10 | jm and a shape factor of 10 to 100, where the shape factor is the measure of the ratio of diameter from particle to particle thickness, for a population of varying size and shape, as measured using the electrical conductivity methods, apparatus, and equations described in US Pat. No. 5,576,617. 2. A milled phyllosilicate mineral according to claim 1, wherein the form factor is in the range of 20 to 70. 3. A milled phyllosilicate mineral according to claim 1, wherein the form factor is in the range of 30 to 60. 4. A milled phyllosilicate mineral according to claim 1, wherein the d50 is in the range of 0.5 to 6 µm. 5. A milled phyllosilicate mineral according to claim 1, wherein the d50 is in the range of 1.0 to 5 µm. 6. A ground phyllosilicate mineral according to claim 1, wherein the d50 is in the range of 1.5 to 4 µm. 7. A milled phyllosilicate mineral according to claim 1, wherein the d50 is in the range of 1.0 to 6.0 µm and the form factor is in the range of 20 to 70. 8. Use of the phyllosilicate ground mineral according to any one of claims 1 to 7 as a pigment for coating or a filler material, or as a part of a coating or filler composition, in the preparation of paper, card , poster, cardboard, writing paper, printing paper, polymers, rubbers, plastics, plastic films, paints, sealants, putties, or ceramics. 9. Composition comprising the ground mineral of phyllosilicate according to any one of claims 1 to 7, for use in obtaining paper, card, poster, cardboard, writing paper, printing paper, polymers, rubbers, plastics, plastic films, paints, sealants, putties, or ceramics 10. Paper comprising the ground phyllosilicate mineral according to any one of claims 1 to 7, wherein the paper is any paper, card, poster, cardboard, such as for example printing paper writing paper. 11. Polymer or rubber comprising the phyllosilicate ground mineral according to any one of claims 1 to 7, wherein the polymer or rubber can be a plastic, such as a plastic film. 12. Paint comprising the ground mineral of phyllosilicate according to any one of claims 1 to 7. 13. Sealant comprising the milled phyllosilicate mineral according to any one of claims 1 to 7. 14. Putty comprising the ground mineral of phyllosilicate according to any one of claims 1 to 7. Ceramic comprising the ground phyllosilicate mineral according to any one of claims 1 to 7.